fix: 大化县政府网公告抓取详情页获取精确发布时间

列表页只有日期(00:00)，改为并发抓取详情页解析 <meta name="PubDate">
获取精确时分秒，失败时保留列表页日期作为 fallback。

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/crawler/parsers.py

@@ -134,6 +134,21 @@ def parse_dahuagov_html(html: str, crawled_at: datetime) -> list[dict[str, Any]]
     return results
 
 
+def parse_dahuagov_detail_pubdate(html: str) -> datetime | None:
+    """从详情页 <meta name="PubDate"> 解析精确发布时间"""
+    soup = BeautifulSoup(html, "html.parser")
+    meta = soup.find("meta", attrs={"name": "PubDate"})
+    if not meta:
+        return None
+    content = meta.get("content", "").strip()
+    for fmt in ("%Y-%m-%d %H:%M:%S", "%Y-%m-%d %H:%M", "%Y-%m-%d"):
+        try:
+            return datetime.strptime(content, fmt)
+        except ValueError:
+            continue
+    return None
+
+
 def _generate_hash(ann: dict[str, Any]) -> str:
     content = (
         f"{ann['title']}|{ann['publish_date'].strftime('%Y-%m-%d')}"